1. Field of the Invention
The present invention relates to a fluid conveying apparatus which is used in conveying a fluid through a flow passage of a small width.
2. Description of the Related Art
Conventionally, as this kind of fluid conveying apparatus, one is known in which there is provided, in a flow passage of a fluid, a platelike cantilever oscillator which oscillates or vibrates with an end portion on an upstream side as seen in a fluid flow direction serving as a fixed end and an end portion on a downstream side serving as a free end.
The velocity of that jet on the downstream side of the oscillator which is generated by the vibration of the above-described oscillator is proportional to the velocity of displacement of the oscillator at the free end thereof. If a conveying capacity of a turbo-machine is compared in terms of a Reynolds number with an impeller diameter serving as the characteristic dimension, it is known that the larger the Reynolds number becomes, the larger the conveying capacity becomes. The same applies to the fluid conveying apparatus which uses a cantilever oscillator. Here, in case the velocity of the jet on the downstream side of the oscillator is equal, the Reynolds number increases with the length of the oscillator. Therefore, the inertia force of the fluid per unit volume in the flow passage increases with the length of the oscillator.
There were prepared an arrangement in which a short oscillator "a" is disposed inside an air flow passage as shown in FIG. 4A and an arrangement in which a long oscillator b is disposed inside an air flow passage as shown in FIG. 4B. Each of the oscillators "a" and b was vibrated so that the velocity U.sub.o of a jet becomes equal to each other. The outlet of the air flow passage was closed in this state and the distribution of the static pressure inside the air flow passage was measured. The result of the measurement of the short oscillator "a" was as shown by line "a" in FIG. 4C, and the result of the measurement of the long oscillator b was as shown by line "b" in FIG. 4C. As compared with the static pressure Pa at the outlet in case the short oscillator "a" was disposed, the static pressure Pb at the outlet in case the long oscillator b was disposed has been found to be higher. The difference in the inertia forces depending on the lengths of the oscillators appears as the static pressures difference (=Pb-Pa) between the two.
As described above, in order to increase the fluid conveying capacity (i.e., the capacity of conveying the fluid), the oscillator should be made as large in length as possible. However, if the length increases, a resonance frequency of the oscillator lowers. Especially, if the flow passage becomes smaller in width, it becomes incapable of securing a sufficient amplitude with a long oscillator. As a result, the velocity of displacement at the free end of the oscillator becomes smaller and the velocity of the jet lowers with a consequent decrease in the static pressure at the outlet. A sufficient conveying capacity will therefore no longer be obtainable.
In view of the above-described points, the present invention has an object of providing an apparatus in which the fluid conveying capacity in a flow passage of narrow width can be improved.